This disclosure relates generally to testing methods and apparatus and, in an example described below, more particularly provides improvements in static gel strength testing.
For prospective cementing operations to be performed in subterranean wells, static gel strength testing is useful to determine how a particular cement composition will perform in downhole conditions. In particular, a static gel strength test can provide information as to how long it will take the cement composition to develop sufficient gel strength to prevent gas percolation through the cement composition.
This information is very useful because, while the cement composition is developing gel strength, its ability to transmit pressure is typically decreasing, thereby decreasing hydrostatic pressure in an annulus (e.g., between a wellbore and a casing or liner) in which the cement composition has been placed. Unless appropriate measures are taken, this decreased hydrostatic pressure could allow gas in an earth formation exposed to the annulus to enter the annulus and percolate upward through the not-yet-hardened cement composition—a situation to be avoided.
Thus, it will be appreciated that improvements are continually needed in the art of static gel strength testing. Such improvements can be useful in testing the static gel strength of cement compositions, or of other slurries, fluids, gels, substances, etc., which develop gel strength.